Numerical Simulation Of Thermal Conductivity Of ?-SiC Nano Films Based On Non-equilibrium Molecular Dynamics

With the emergence of artificial intelligence and 5G concept,the research and development of chips and semiconductor components become more and more important.SiC is the third batch of rising semiconductor materials which has excellent performance in the aspects of working voltage,carrying current,working frequency,material temperature,which makes it receive more and more attention in the field of semiconductor.At present,it has been widely used in electric vehicles and new energy industries.Among various allotropes of SiC,?-SiC has the best electronic properties and the most stable structure compared with other shapes.Therefore,the preparation,modification,optical,electrical and mechanical properties of ?-SiC films are studied increasingly.In the study of material modification,in order to further improve the conductivity,nitrogen atoms can be doped into the ?-SiC film structure to achieve but this to some extent weakens the thermal conductivity of the material.Thermal conductivity influences device performance and thermal design directly.Moreover,compared with bulk materials,the thermal conductivity of film materials shows specificity and the thermal conductivity will be reduced,so the research on the thermal conductivity of ?-SiC film becomes more important and urgent.In this paper,the thermal conductivity of ?-SiC film and nitrogen doped ?-SiC film is studied by numerical simulation,non-equilibrium molecular dynamics and compass force field.The thermal conductivity of ?-SiC films with different thickness and temperature is studied.When the film thickness increases from 3.426 nm to 6.905 nm at room temperature,the thermal conductivity of ?-SiC film increases from 5.054 Wm-1K-1 to 9.654 Wm-1K-1.The thermal conductivity of ?-SiC film increases with the increase of the thickness.In the nano scale,the decreasing of specific surface area and the weakening boundary phonon scattering increase the thermal conductivity of the film with the increasing of the thickness which shows obvious scale effect.For ?-SiC films with a thickness of 5.165 nm,when the temperature changes from 300 K to 1000 K,the thermal conductivity of ?-SiC films is between 7.478 Wm-1K-1 and 7.315 Wm-1K-1,which decreases slowly with the increase of temperature.The average phonon group velocity plays a decisive role in the thermal conductivity of the material.As a result,the thermal conductivity of ?-SiC film decreases with the increase of temperature.It is found that the thermal conductivity of ?-SiC films with the same thickness of doped N atom at room temperature is lower than that of undoped ?-SiC films.When the concentration of doped N atom is 0.195% and thickness is the same of undoped film that thickness increasing from 3.426 nm to 6.905 nm,the film thermal conductivity increases from 4.303 Wm-1K-1 to 6.798 Wm-1K-1,which has the same change trend and be smaller than that of film thermal conductivity undoped.At room temperature,for the 4.296 nm thickness N-doped ?-SiC films,the thermal conductivity of the films decreased from 6.417 Wm-1K-1 to 4.521 Wm-1K-1 when the doping concentration changes from 0.039% to 0.781%,which decreases with the increasing of the nitrogen concentration.For ?-SiC films with 0.195% doped nitrogen atom concentration and 4.296 nm film thickness,temperature changing from 300 K to 800 K,the thermal conductivity decreases from 5.527 Wm-1K-1 to 4.764 Wm-1K-1.Under the condition of nitrogen doping,the trend of thermal conductivity decreases with the increasing of temperature is more obvious than that of undoped films for lattice distortion caused by doping and the mechanism of electron phonon scattering in the system.